Microbial nitrogen loss by coupled nitrification to denitrification and anammox in a permeable subterranean estuary at Gloucester Point, Virginia.

The nitrogen (N) loss processes have not been well examined in subterranean estuaries (STEs) between land and sea. We utilized a N isotope tracer method, q-PCR, and high-throughput sequencing to reveal the activities, abundances, and community compositions of N loss communities in a STE in Gloucester Point, Virginia, US. The highest activities, abundances and diversity of denitrifiers and anammox bacteria were detected at 50-60 cm depth in the aerobic-anaerobic transition zone (AATZ) characterized by sharp redox gradients. nirS-denitrifiers and anammox bacteria were affiliated to 10 different clusters and three genera, respectively. Denitrification and anammox played equal roles with an estimated N loss of 13.15 mmol N m day. A positive correlation between ammonia oxidizing prokaryote abundances and DO as well as NO suggested that nitrification produces NO which supports the hotspot of denitrification and anammox within the AATZ. Overall, these results highlight the roles of N loss communities in STEs.